Object snap

Faster operation of the drawing application can be achieved when the
objects cannot be moved or placed at each pixel but only at a multiple
of a pixel. Values may be every 6th, 8th, 10th, 12th, 20th or so pixel.
The user has to concentrate less, the bigger the object snap. The pixel
snap and the object snap have to be adjusted for sensible numbers.

Grid

drawing a grid poses the same problems as the snap does. Grid lines
should have a certain gap between them. The grid could be placed at
the object snap or a multiple.

finding sensible numbers

after introducing the snap, the numbers are considered even at the small scale.
Still some care has to be taken when drawing a grid or ruler.
examples with 0.2 and 0.002 distance :